The present invention relates to polishing apparatuses, and relates in particular to a polishing apparatus to provide consistent polishing by supplying polishing solution consistently regardless of disturbances in a polishing solution supply facility.
Advances in integrated circuit devices in recent years have been made possible by ultra fine wiring patterns and interline spacing. The trend towards high density of circuit integration leads to a requirement of extreme flatness of a substrate surface to satisfy the shallow depth of focus of stepper printer in photolithographic reproduction of microcircuit patterns.
One method of producing such a flat surface on a semiconductor wafer surface is to use a polishing apparatus having a polishing tool (for example, a polishing table having a polishing cloth) and a wafer holding section for holding the wafer and pressing and sliding the wafer against the polishing tool while supplying a polishing solution to the polishing surface. Such an apparatus can perform not only mechanical polishing but also chemical polishing using an alkaline or acidic polishing solution.
Polishing solution is normally prepared by mixing a stock solution and a dilution liquid in a mixing tank, which is used to supply a mixed solution through a delivery pipe to the solution nozzle of the polishing apparatus. The polishing facility may have associated cleaning mechanisms. When a plurality of polishing apparatuses are arranged in parallel to perform production of substrates, one solution supply device is normally provided for several polishing apparatuses. Also, in a production plant based on an even greater number of polishing apparatuses, consideration is given to a polishing solution delivering system having a stem pipe (circulating pipe) extending from one mixing tank and circulating around the plant and branch pipes branching from the stem pipe for delivering solution to each polishing apparatus, in an effort to reduce the operating and facility costs.
However, in such a conventional technology to supply the solution to each polishing apparatus by using a circulation pump, it is necessary to select a delivery capacity for the circulation pump so that the capacity would be sufficient to deliver a necessary quantity of solution at full plant operation, thus resulting in a high facility cost. Furthermore, because of fluctuations in solution supply rate caused by pressure changes in the delivery pipes due to changes in the number of operating polishing apparatuses, it is difficult to maintain a stable flow of solution of a given concentration. This affects the quality of polished products produced at various polishing apparatuses within the plant. It will be necessary to provide expensive flow control devices and complex process control methodology to overcome such flow rate fluctuation to provide a steady flow of polishing solution of a consistent quality to each polishing apparatus.
It is an object of the present invention to provide a polishing apparatus that enables production of a uniform quality of polished products by supplying a polishing solution consistently without being affected by any disturbances in the solution supply source.
The object has been achieved by providing a polishing apparatus comprising: a polishing section for polishing a workpiece by pressing the same against a polishing tool; a solution piping assembly to be connected to an external solution supply device for transferring a polishing solution therefrom to the polishing section; and a solution suction device provided in the solution piping assembly for introducing the polishing solution from the solution supply device to the polishing section at a desired flow rate.
Accordingly, an independent polishing unit with high flexibility is presented that can operate regardless of the presence or absence of fluid transport means for the polishing solution in the external polishing solution source. Even if a fluid transport means is to be provided in the external source of polishing solution, it is not necessary to choose an excessive capacity for the fluid transport means, and it is only necessary to operate a fluid transport means to suit the polishing load of polishing apparatuses. Thus, wasteful facility and operating costs can be eliminated.
The solution piping assembly may be provided with a flow control device for adjusting flow rates of polishing solution through the solution piping assembly. Accordingly, polishing solution can be supplied at a flow rate to suit the needs of individual polishing apparatuses, thereby providing stable and accurate flow control.
The solution piping assembly may be provided with a smoother for smoothing out pulsation of the polishing solution flowing therethrough. Accordingly, even when flow pulsation is produced in the fluid transport means over small time intervals, such as in peristaltic pumps, stable flow of polishing solution can be supplied.
The present polishing apparatus can supply polishing solution consistently regardless of any disturbances in the solution supply device so that a polishing operation can be carried out correctly at individual polishing apparatuses. When an external fluid transport device is utilized in the external solution supply source, it is not necessary to design an excessive capacity so that wasteful facilities and operating costs can be eliminated, thus resulting in integration of a solution supply facility even in a relatively large production plant having a large number of polishing apparatuses operating therein. Capital cost and space allowances can thus be lowered to bring genuine benefits to industries concerned with advanced semiconductor device production.
The polishing apparatus may be assembled in a polishing unit together with a storing section for storing a workpiece, and a transporting device for transporting the workpiece between the polishing apparatus and the storing section.
The polishing apparatus may be assembled in a polishing system together with a solution supply device, and a solution distribution pipe for distributing a polishing solution from the solution supply device to the polishing apparatus, in which the solution piping assembly is connected to the solution distribution pipe.